NEW YORK (Reuters Health) - Despite having equal access to health care through military health insurance, black women with breast cancer are less likely than white women to receive certain aggressive treatments, according to the findings of a new study.

The researchers, based at Walter Reed Army Medical Center and the National Cancer Institute, compared treatments for breast cancer among 2300 white women and nearly 400 black women who had health insurance through the Department of Defense, either as members of the military or as members' beneficiaries.

Black and white women were equally likely to have either a breast-removing surgery (a mastectomy) or a surgery that leaves more of the breast intact.

However, black women who had tumors that had spread beyond the breast were less likely to receive chemotherapy or hormonal therapy in addition to the surgery.

Previous work has identified racial disparities among women with breast cancer, in particular, finding that black women are less likely to receive aggressive treatment and more likely to die from the disease (see Reuters Health reports from March 26, 2008 and July 25, 2011).

The reasons for these inequities range from higher rates of poverty to lower rates of health insurance to a greater likelihood of having hypertension (see Reuters Health report from March 12, 2009).

But in this case, "you can take off the table access to health care," said Colonel Craig Shriver, the chief of the breast care center at Walter Reed Army Medical Center and one of the authors of the study. "One of the main features of the military health care system...is access is not a problem."

Shriver's group found, nonetheless, that after breast surgery, the black patients whose cancer had spread beyond the breast were 60 percent less likely to receive chemotherapy and 50 percent less likely to receive hormonal therapy than white patients with similar cancers.

Black women who had tumors confined to the breast were just as likely to receive chemotherapy and hormonal therapy as white women.

The study, which was published in the journal Cancer, did not determine whether these differences in treatment resulted in better or worse outcomes for the patients.

Shriver told Reuters Health he doesn't know why the treatment differed between the black and white patients with advanced cancers.

One potential explanation "is that they're being offered the treatment, but they're not accepting it," Shriver offered.

In that situation, cultural factors might be influencing women's choices.

"We should explore further what those may be," Shriver said.

There is also the possibility of a data collection problem. If a patient has private insurance in addition to insurance through the Department of Defense, the private insurance would be billed first, and Shriver's team would not be able to track that woman's treatment.

Dr. Ismail Jatoi, a professor at the University of Texas Health Science Center in San Antonio, agreed that he'd like to see more research to probe the reasons for different breast cancer treatments.

"I think it's important to understand why we're seeing these sorts of variations," said Jatoi, who was not involved in this study. "It will add more to our widening knowledge of health care disparities and where we should be going to reduce health disparities."